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Old 08-20-2015, 04:08 PM   #11
TerryH
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Default Re: 30 mph txt

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Originally Posted by JohnnieB View Post
If your tires are truly 20" tall and you have 12.44:1 gears, your motor is spinning at 5,018 RPM at 24 MPH, so going from 42V to 48V will kick the RPM up by 16.7% to 5,856 RPM, which is 28.0 MPH

At 42V, your motor and 8:1 gears with 20" tires will do 37.3 MPH mathematically.
At 48V, your motor and 8:1 gears with 20" tires will do 43.5 MPH mathematically.

However, going from 12.44:1 gear to 8:1 gears will reduce available torque where rubber meets road by 36%, so you won't reach the mathematical speeds listed above. Without having any torque vs RPM data for your motor, I cannot even guess what the actual speeds would be.

Ironically, Terry and I are running the same motor (D&D ES-76-51), but in two very different carts.

I run 17" tires and 12.44:1 gears at 42V and get 28 MPH (6,900 RPM)
I'm not sure what his tire height is, but his tow cart isn't lifted so they are less than 20" and he is running 6:1 gears at 48V and gets 40+ MPH. (Probably at about half the RPM my motor spins at top speed)

His cart will run circles around mine on the top end, yet has enough low end torque to tow his dragster, but if you tied our cart's rear bumpers together and floored both, my cart would pull his backwards or wear out the tires trying to.

The reason is because the ES-76-51 has roughly the same RPM for the applied voltage as a stock PDS motor, but about 30% more torque.


Hi-Speed motors and Hi-Speed gears (and/or tall tires) don't play well together.
Agree ^^

The correct choice of motor/controller/batteries/cables/gears/tires etc... will result in a combo that will perform well and live. My DCX600 controller allows amperage to spike well above the advertised 600. I've seen mine pull more than 800. Amps = torque. Volts = rpm. So the D&D motor is able to pull enough amps to still provide good low end grunt even with the 6:1 gears on our cart. The amps and voltage coupled with the gear allows the cart to tow the dragster with ease and still have a terminal speed of 43 mph which equates to about 4400 rpm with my 20" rear tires.
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Old 08-21-2015, 08:03 AM   #12
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Default Re: 30 mph txt

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Originally Posted by TerryH View Post
The correct choice of motor/controller/batteries/cables/gears/tires etc... will result in a combo that will perform well and live.

My DCX600 controller allows amperage to spike well above the advertised 600. I've seen mine pull more than 800. Amps = torque. Volts = rpm. So the D&D motor is able to pull enough amps to still provide good low end grunt even with the 6:1 gears on our cart. The amps and voltage coupled with the gear allows the cart to tow the dragster with ease and still have a terminal speed of 43 mph which equates to about 4400 rpm with my 20" rear tires.
Truer words have seldom been spoken.

However, with SepEx motors, you have to add another item to the list of things that have to match. Field Mapping.

I lost a little speed when I went from a DCX to a XCT controller, but got it back and then some when I obtained a field map specifically written for a ES-76-51.

If your DCX600 ever gives up the ghost, replace it with a XCT500.
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Old 08-21-2015, 03:23 PM   #13
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Default Re: 30 mph txt

Terry H and Jonnie B are incredible. Had to put on my engineers cap to get into the field mapping.it should be done in a week or 2. Thank you guys, I'll post the new results when I'm finished. Thanks again
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Old 08-21-2015, 03:57 PM   #14
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Default Re: 30 mph txt

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Terry H and Jonnie B are incredible. Had to put on my engineers cap to get into the field mapping.it should be done in a week or 2. Thank you guys, I'll post the new results when I'm finished. Thanks again
In a nutshell, field mapping is what makes a SepEx (SEParately EXicited) motor so versatile.

With a SepEx motor you can change it from a High-Torque motor to a High-speed motor during operation by changing the field excitation (amount of amps flowing through the field windings), while with a Series wound motor, whatever it is wound for when it is made is what you've got.
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Old 08-21-2015, 04:10 PM   #15
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Default Re: 30 mph txt

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In a nutshell, field mapping is what makes a SepEx (SEParately EXicited) motor so versatile.

With a SepEx motor you can change it from a High-Torque motor to a High-speed motor during operation by changing the field excitation (amount of amps flowing through the field windings), while with a Series wound motor, whatever it is wound for when it is made is what you've got.

Do you know how the emp speed/torque motors work on series motors? I found a used 36v one for cheap.

I emailed emp about just using it for speed, and they said that motor wasn't designed for 48v or high speed gears.

I can see the high speed gears, but the cart it came out of was running it on 48v. The only problems he had was burning out his factory forward reverse.


Don't people also take stock 36v carts to 48 and use the factory motor?
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Old 08-22-2015, 08:19 AM   #16
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Default Re: 30 mph txt

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Originally Posted by Jeffreynmandy View Post
1. Do you know how the emp speed/torque motors work on series motors? I found a used 36v one for cheap.

2. I emailed emp about just using it for speed, and they said that motor wasn't designed for 48v or high speed gears.

3. I can see the high speed gears, but the cart it came out of was running it on 48v. The only problems he had was burning out his factory forward reverse.


4. Don't people also take stock 36v carts to 48 and use the factory motor?
1. Whether a motor is a Hi-Torque motor, or a Hi-Speed motor, or something in between, is determined by the relative magnetic strength generated by the moving electromagnets (Armature) and non-moving electromagnets (Field aka Stator).

If the Field's magnetic field is relatively strong when compared to the Armature's magnetic field, the motor develops more torque at lower RPM and is called a Hi-Torque motor. The net result is that the cart tends to have rapid acceleration from a standstill and lots of low speed pulling power, but won't go very fast.

If the Field's magnetic field is relatively weak when compared to the Armature's magnetic field, the motor develops more torque at higher RPM and is called a Hi-Speed motor. The net result is the cart has less acceleration and pulling power, but will go faster.

The same amount of amps flow through both the Armature and Field in a series wound motor, in fact it is the same current. By bypassing part of the field windings, you can transform a Hi-Torque series motor into a Hi-Speed series motor and I suspect that is what EMP does.

2. EMP know far more about the motors they build than anybody else does, so I'll accept what they say as gospel. Of course, stating that the motor is not designed for 48V or high speed gears doesn't mean it won't work with them, only that if you do it, it voids any and all warranties by, and culpability of, the manufacturer if something bad happens.

3. The mechanical F/R switch is the weak link in a series drive system, but there are heavy-duty switch assemblies out there that fair better in upgraded carts and there are reversing contactors that work even better.

4. Yes, most stock cart motors tolerate running at 48V fairly well, but most stock cart motors are middle of the road winds and when you get into Hi-Speed or Hi-Torque winds, the tolerances change.

On the other hand, heat is what kills motors and motors running on 48V tend to run cooler than those running on 36V, if the workload stays the same.

Like Terry said "The correct choice of motor/controller/batteries/cables/gears/tires etc... will result in a combo that will perform well and live."
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Old 08-22-2015, 09:17 AM   #17
TerryH
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Default Re: 30 mph txt

My experience with EMP especially and motor manufacturers in general is that they are ultra careful about anything that might make them liable for anything. Not a bad idea in today's litigious society but that doesn't mean that it won't work. Nothing ventured, nothing gained. Monitor motor temp and let her rip.
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Old 08-22-2015, 09:39 AM   #18
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Default Re: 30 mph txt



I've never spoken with EMP, but Terry hit the nail on the head about motor manufacturers being cautious and having good reason to be that way.

Just look at the owners manual for anything. More than half of it is usually warnings and cautions and disclaimers.
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Old 08-22-2015, 10:00 AM   #19
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Default Re: 30 mph txt

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Originally Posted by JohnnieB View Post


I've never spoken with EMP, but Terry hit the nail on the head about motor manufacturers being cautious and having good reason to be that way.

Just look at the owners manual for anything. More than half of it is usually warnings and cautions and disclaimers.
I talked to uber conservative EMP about building a motor for the dragster. You can imagine their reaction when I told them what I had in mind.
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Old 08-22-2015, 10:41 AM   #20
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Default Re: 30 mph txt

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Originally Posted by TerryH View Post
I talked to uber conservative EMP about building a motor for the dragster. You can imagine their reaction when I told them what I had in mind.
I had an interesting conversation with Vic at D&D. Not about what I wanted to do, but what I was doing.
He found it difficult to believe I was getting over 28 MPH with a ES-76-51 running on 42V turning stock height tires thru stock gears.
The irony is that I thought my tires were 18.3" (MTD from Carlisle website) tall instead of the 17.04" (Measured) they actually are, so I was spinning it at 7k rather that the 6.5k I thought I was while I was talking to him.


It looks like you finally did find a motor builder that is almost as crazy as you are.

Love the double brushes.
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